There is a sheet postprocessing apparatus for carrying out a processing of stapling or punch hole forming, binder mounting or the like for sheets discharged from a copier or the like. The sheet postprocessing apparatus are constituted to be included in or connected to a copier and operate in cooperation with the copier in accordance with settings. After supplying one set of sheets from a copier or the like onto a sheet table, a postprocessing of stapling or the like is carried out.
JP-A-2002-241036 discloses an example of sheet aligning means for aligning a position of a sheet on a sheet table in a sheet postprocessing apparatus. The sheet postprocessing apparatus of JP-A-2002-241036 includes a pusher sliding from a transverse wall face of the table in a direction of a center of the table, and a rotating brush hung above the table for pushing a side face of a sheet introduced to the table by the pusher to align a position thereof in a transverse direction and aligning a position thereof in a longitudinal direction by sweeping a surface of the sheet by the rotating brush.
When a sheet receiving portion (sheet table) of the sheet postprocessing apparatus is arranged horizontally, a width of the apparatus is increased and therefore, it is general to arrange the sheet table to be erected skewedly. In this case, although a sheet supplied from a processing apparatus of a copier or the like at a prestage to the sheet postprocessing is dropped onto the inclined sheet table to be laminated thereon, the sheet passing through the copier or the like at the prestage is curled in almost all the cases to be brought into a state in which both front and rear ends thereof are warped.
Although when the sheet table is arranged horizontally, even when the sheet is curled, the sheet can be recovered to a flat attitude by its own weight and therefore, the problem described below is posed comparatively rarely, when the sheet table is arranged vertically, also the sheet is constituted by a vertical attitude and therefore, there is a case in which the curl is promoted by a gravitational force thereof and intervals of both front and rear end portions (both up and down end portions) of laminated sheets are increased to produce gaps therebetween. Further, when the gap is produced at an end portion on a rear side (upper side), there is a case in which a successively fed sheet advances to between sheets on the sheet table and cannot be moved down to a predetermined position to bring about sheet jamming.